You can get penalties from image owner. However, it will not be noticeable by him until you will have an enormous blog that everyone knows about. On the Google side... Well, you better have some minimal Photoshop skills to wrap a picture with color saturation or make other color changes so this will become a "unique" picture.

Overall, i recommend at least give a credit for a website you got a picture from. That way you will not encounter any law or whatever (be sure to check that website Policy - possibly they want a Do-Follow link when you want to use some materials from them)

Have you ever wondered if it was legal to use any image you found online through a Google search? Some of us want to use an image we find on Google for our website, brochures or blogs, but is that okay? You’ve probably also heard us say that you need to add an image to your articles or pages for SEO purposes, but you may not be a photographer or want to spend money purchasing images. So can you just jump on Google and use any image found there? Here’s the low down…